Genetic Manipulation
Resumen
On a shelf in a plant laboratory there are two hundred sealed jars, and in each jar a small green plant is growing on a bed of clear jelly. The plants are the same height, the same shade, the same shape, and they came from one parent plant that is still alive somewhere else. In a building on the other side of the same city a steel vessel is stirring a warm broth of bacteria, and those bacteria are quietly manufacturing a human protein that no bacterium has ever needed. Neither of those rooms is doing anything to an organism that biology forbids. Both are using the same fact: inherited information is a chemical, and a chemical can be copied and it can be moved.
This lesson separates the two things that fact allows. Copying an organism gives you individuals with the same genes as the one you started from, and the specification names three techniques for doing it. Moving one gene into an organism gives you something else entirely: a living thing that keeps all of its own genes and gains a single instruction it was never going to inherit. You will work through both, follow a gene into a crop plant and see why the harvest gets bigger, and finish on the part of this topic that carries the most marks in the long run, which is being handed information you have never seen about one of these techniques and being asked to reach a judgement you can defend. One section of this topic is printed as Extension Tier content, and the lesson marks that line exactly where the specification puts it.
Objetivos
- Modern cloning techniques include: tissue culture - using small groups of cells from part of a plant; embryo transplants - splitting cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers; adult cell cloning - the nucleus is removed from an unfertilised egg cell and the nucleus from an adult body cell, eg a skin cell, is inserted into the egg cell. An electric shock then acts as the catalyst for the egg cell to begin to divide to form embryo cells. These embryo cells contain the same genetic information as the adult skin cell. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
- In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms: enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus; the vector is used to insert the gene into the required cells.
- Genes can also be transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.
- Crops that have had their genes modified in this way are called genetically modified (GM) crops. GM crops include ones that are resistant to insect attack or to herbicides.
- GM crops generally show increased yields.
- Concerns about GM crops include the effect on populations of wild flowers and insects, and uncertainty about the effects of eating GM crops on human health. Students should be able, when provided with appropriate information, to interpret information about cloning techniques and genetic engineering techniques and to make informed judgements about issues concerning cloning and genetic engineering, including GM crops.
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Evaluación de la lección
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- Which cloning technique uses a small group of cells taken from part of a plant? A. Embryo transplants B. Tissue culture C. Adult cell cloning D. Sexual reproduction Answer: B
- In adult cell cloning, what is removed from the unfertilised egg cell? A. The cytoplasm B. The cell membrane C. The nucleus D. The mitochondria Answer: C
- In adult cell cloning, what acts as the catalyst that makes the egg cell begin to divide? A. An electric shock B. Fertilisation by a sperm cell C. A rise in temperature D. Adding a plant growth substance Answer: A
- Which of these is a concern named in the specification about growing GM crops? A. GM crops generally give lower yields B. GM crops cannot be made resistant to herbicides C. GM crops may affect populations of wild flowers and insects D. GM crops are clones of one another Answer: C
- Extension Tier. In genetic engineering, what is usually used as a vector? A. An enzyme B. A ribosome C. A bacterial plasmid D. A red blood cell Answer: C
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